Air Convection on a Micro Hotplate Gas Sensor

Monitoring of indoor CO2 concentration is of particular interest to detect room occupancy in order to optimize power consumptions of building. One approach to monitor the indoor CO2 concentration is to use optical detection using specific absorption lines of CO2 molecules in the infrared domain close to 4.2 µm. Such optical sensors include a detector, typically a micro-bolometer, an IR source (the hotplate). All these components are made in well known planar Si technology using the MEMS approach. To optimize the consumption of the filament geometry (conductive track), we have to introduce the conductive and convective thermal exchanges in air around the micro-hotplate using COMSOL's Heat Transfer Module. We deduce an explicit thermal flux law.